U.S. patent number 7,237,441 [Application Number 10/544,669] was granted by the patent office on 2007-07-03 for ultrasonic type fluid measurement device.
This patent grant is currently assigned to Matsushita Electric Industrial Co., Ltd.. Invention is credited to Yoshinori Inui, Shigeru Iwanaga, Hajime Miyata, Yukio Nagaoka, Yasuhiro Umekage.
United States Patent |
7,237,441 |
Umekage , et al. |
July 3, 2007 |
Ultrasonic type fluid measurement device
Abstract
An ultrasonic fluid measurement instrument is capable of highly
accurate fluid measurement. A measurement part is provided forming
a plurality of split channels partitioned by partition boards
halfway across a fluid channel, and at least a pair of ultrasonic
transmitter-receivers for transmitting ultrasonic waves into the
fluid flowing through the split channels and receiving ultrasonic
waves that have passed through the fluid. Further, an arithmetic
unit calculates the flow velocity and/or flow volume of the fluid
according to the propagation time of the ultrasonic waves. The
measurement part further includes an approach channel for
preliminarily rectifying the fluid flowing to the split
channels.
Inventors: |
Umekage; Yasuhiro (Shiga,
JP), Inui; Yoshinori (Nara, JP), Nagaoka;
Yukio (Kyoto, JP), Miyata; Hajime (Nara,
JP), Iwanaga; Shigeru (Nara, JP) |
Assignee: |
Matsushita Electric Industrial Co.,
Ltd. (Osaka, JP)
|
Family
ID: |
32911435 |
Appl.
No.: |
10/544,669 |
Filed: |
February 24, 2004 |
PCT
Filed: |
February 24, 2004 |
PCT No.: |
PCT/JP2004/002119 |
371(c)(1),(2),(4) Date: |
August 04, 2005 |
PCT
Pub. No.: |
WO2004/074783 |
PCT
Pub. Date: |
September 02, 2004 |
Prior Publication Data
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Document
Identifier |
Publication Date |
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US 20060201259 A1 |
Sep 14, 2006 |
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Foreign Application Priority Data
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Feb 24, 2003 [JP] |
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2003-045616 |
Mar 17, 2003 [JP] |
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2003-071395 |
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Current U.S.
Class: |
73/861.27 |
Current CPC
Class: |
G01F
1/667 (20130101); G01F 1/662 (20130101) |
Current International
Class: |
G01F
1/84 (20060101) |
References Cited
[Referenced By]
U.S. Patent Documents
Foreign Patent Documents
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1116877 |
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Feb 1996 |
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CN |
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1136844 |
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Nov 1996 |
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CN |
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5-093637 |
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Apr 1993 |
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JP |
|
9-043015 |
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Feb 1997 |
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JP |
|
9-145438 |
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Jun 1997 |
|
JP |
|
11-051735 |
|
Feb 1999 |
|
JP |
|
00/55581 |
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Sep 2000 |
|
WO |
|
Primary Examiner: Patel; Harshad
Attorney, Agent or Firm: Wenderoth, Lind & Ponack,
L.L.P.
Claims
The invention claimed is:
1. An ultrasonic fluid measurement instrument comprising: a fluid
channel having a width; a measurement part including: an approach
channel portion located at an upstream side of said measurement
part and extending into said fluid channel to one half of the width
of said fluid channel; and a split channel portion including at
least one partition board, said at least one partition board
dividing said split channel portion into at least two channels that
are open at opposite ends to allow fluid to flow therethrough, said
split channel portion being located downstream of said approach
channel; a pair of ultrasonic transmitter-receivers operable to
transmit ultrasonic waves into the fluid flowing through the at
least two channels of said split channel portion, and receive the
ultrasonic waves from the fluid flowing through the at least two
channels of said split channel portion; and an arithmetic unit
operable to calculate at least one of flow velocity of the fluid
and flow volume of the fluid based on a propagation time of the
ultrasonic waves transmitted and received by said pair of
ultrasonic transmitter-receivers, wherein: said approach channel
portion preliminarily rectifies the fluid prior to the fluid
flowing to said split channel portion; said ultrasonic
transmitter-receivers are disposed at a side wall of said
measurement part and at opposite sides of said split channel
portion; and one of said ultrasonic transmitter-receivers is
located at an upstream side of said split channel portion and
another of said ultrasonic transmitter-receivers is located at a
downstream side of said split channel portion.
2. The ultrasonic fluid measurement instrument as claimed in claim
1, wherein said fluid channel and said measurement part are
separate structures.
3. The ultrasonic fluid measurement instrument as claimed in claim
1, wherein said approach channel portion has a fixed
cross-sectional area.
4. The ultrasonic fluid measurement instrument as claimed in claim
1, wherein a length of said approach channel portion is longer than
a height of said measurement part.
5. The ultrasonic fluid measurement instrument as claimed in claim
1, wherein a thickness of said at least one partition board is less
than a wavelength of the ultrasonic waves transmitted from said
pair of ultrasonic transmitter-receivers.
6. The ultrasonic fluid measurement instrument as claimed in claim
1, wherein one of said at least one partition board is positioned
in a center of an ultrasonic transmitting region of said pair of
ultrasonic transmitter-receivers.
7. The ultrasonic fluid measurement instrument as claimed in claim
1, wherein said at least one partition board is an odd number of
partition boards forming the at least two channels and one of said
at least one partition board is centrally located and positioned in
a center of an ultrasonic transmitting region of said pair of
ultrasonic transmitter-receivers.
8. The ultrasonic fluid measurement instrument as claimed in claim
1, wherein said approach channel portion is arranged to extend into
an upstream chamber of said fluid channel.
9. The ultrasonic fluid measurement instrument as claimed in claim
1, wherein at least a part of a surface of the at least two
channels of said split channel portion is surface-treated with a
nonviscous material.
10. The ultrasonic fluid measurement instrument as claimed in claim
1, wherein a portion of the side wall of said measuring part on
which said pair of ultrasonic transmitter-receivers is mounted is
covered with a perforated plate.
11. The ultrasonic fluid measurement instrument as claimed in claim
1, wherein a portion of the side wall of said measuring part on
which said pair of ultrasonic transmitter-receivers is mounted is
covered with a wire mesh having 50 to 500 openings.
Description
This application is a U.S. National Phase application of PCT
International Application PCT/JP2004/002119.
BACKGROUND OF THE INVENTION
1. Field of the Invention
The present invention relates to an ultrasonic fluid measurement
instrument that measures flow velocity and flow volume of fluid
such as gas and water utilizing the propagation time of ultrasonic
waves.
2. Description of the Related Art
The conventional ultrasonic fluid measurement instrument that
measures flow volume and the like utilizing the propagation time of
ultrasonic waves is provided with a measurement part halfway across
the fluid channel to measure the flow velocity of fluid flowing
through this measurement part according to the propagation time of
ultrasonic waves between ultrasonic transmitter-receivers. The flow
volume is obtained by multiplying the flow velocity measured above,
by the cross-sectional area of the channel in the measurement part,
and by a given correction coefficient.
The most significant element that enables highly accurate
measurement for flow volume and the like is a flowing state of
fluid in the above-mentioned measurement part. In other words, a
turbulent fluid flow in the measurement part causes disruption in
ultrasonic propagation, disabling highly accurate measurement.
Under the circumstances, the following arrangement has been devised
conventionally as disclosed in Japanese Patent Unexamined
Publication No. H09-43015. That is, a measurement part is
rectangular with its rectangle cross-section, and the short side is
partitioned by partition boards to form plural flat split channels
in parallel with the long side. The flat split channels effectively
make the fluid flow into a laminar flow, namely a two-dimensional
stable flow.
Meanwhile, the measurement part composed of the above-mentioned
plural flat split channels is significantly large in width compared
to the fluid channel for admitting fluid.
Therefore, the measurement part is connected to the fluid channel
through a tapered connection part with a larger width at the
downstream side.
As a result, this tapered connection part causes a turbulent flow
in the fluid, and thus the fluid becomes resistant to flowing
evenly through all the split channels, resulting in decreasing
measurement accuracy.
The present invention, aiming at solving such conventional
problems, provides an ultrasonic fluid measurement instrument that
enables highly accurate measurement of fluid flow.
SUMMARY OF THE INVENTION
An ultrasonic fluid measurement instrument according to the present
invention is equipped with a fluid channel having a measurement
part formed with plural split channels partitioned by partition
boards halfway across the channel; at least a pair of ultrasonic
transmitter-receivers that transmit ultrasonic waves into fluid
flowing through the above-mentioned split channels, and receive
ultrasonic waves that have passed through the fluid; and an
arithmetic unit for calculating at least one of the flow velocity
and flow volume of fluid according to the propagation time of
ultrasonic waves generated by the above-mentioned ultrasonic
transmitter-receivers. The above-mentioned measurement part is
provided with an approach channel for preliminarily rectifying
fluid flowing to the split channels.
Another ultrasonic fluid measurement instrument according to the
present invention is equipped with a fluid channel; a measurement
part composed separately from the fluid channel, formed with plural
split channels partitioned by partition boards; at least a pair of
ultrasonic transmitter-receivers that transmit ultrasonic waves
into fluid flowing through the above-mentioned split channels, and
receive ultrasonic waves that have passed through the fluid; and an
arithmetic unit for calculating at least one of the flow velocity
and flow volume of fluid according to the propagation time of
ultrasonic waves generated by the above-mentioned ultrasonic
transmitter-receivers. The above-mentioned measurement part is
provided with an approach channel for preliminarily rectifying
fluid flowing to the split channels.
BRIEF DESCRIPTION OF THE DRAWINGS
FIG. 1 shows a longitudinal sectional view of an ultrasonic fluid
measurement instrument according to exemplary embodiment 1 of the
present invention.
FIG. 2 shows a transverse sectional view of an ultrasonic fluid
measurement instrument according to exemplary embodiment 1 of the
present invention.
FIG. 3 shows a longitudinal sectional view of an ultrasonic fluid
measurement instrument according to exemplary embodiment 2 of the
present invention.
FIG. 4 shows a longitudinal sectional front view of an ultrasonic
fluid measurement instrument according to exemplary embodiment 3 of
the present invention.
FIG. 5 shows a longitudinal sectional front view of an ultrasonic
fluid measurement instrument according to exemplary embodiment 4 of
the present invention.
FIG. 6 shows a transverse sectional view of an ultrasonic fluid
measurement instrument according to exemplary embodiment 5 of the
present invention.
FIG. 7 shows a transverse sectional view of an ultrasonic fluid
measurement instrument according to exemplary embodiment 6 of the
present invention.
FIG. 8 shows a longitudinal sectional view of an ultrasonic fluid
measurement instrument according to exemplary embodiment 7 of the
present invention.
FIG. 9 shows a transverse sectional view for illustrating the
actions of an ultrasonic fluid measurement instrument according to
exemplary embodiment 7 of the present invention.
FIG. 10 shows a longitudinal sectional view of an ultrasonic fluid
measurement instrument according to exemplary embodiment 8 of the
present invention.
FIG. 11 shows a longitudinal sectional view of an ultrasonic fluid
measurement instrument according to exemplary embodiment 9 of the
present invention.
FIG. 12 shows a longitudinal sectional view of an ultrasonic fluid
measurement instrument according to exemplary embodiment 10 of the
present invention.
FIG. 13 shows a longitudinal sectional view of an ultrasonic fluid
measurement instrument according to exemplary embodiment 11 of the
present invention.
FIG. 14 shows a transverse sectional view of an ultrasonic fluid
measurement instrument according to exemplary embodiment 11 of the
present invention.
FIG. 15 shows a longitudinal sectional view of an ultrasonic fluid
measurement instrument according to exemplary embodiment 12 of the
present invention.
FIG. 16 shows a longitudinal sectional view of the measurement part
of an ultrasonic fluid measurement instrument according to
exemplary embodiment 13 of the present invention.
FIG. 17 shows a longitudinal sectional view of an ultrasonic fluid
measurement instrument according to exemplary embodiment 14 of the
present invention.
FIG. 18 shows a longitudinal sectional view of an ultrasonic fluid
measurement instrument according to exemplary embodiment 15 of the
present invention.
FIG. 19 shows a longitudinal sectional view of an ultrasonic fluid
measurement instrument according to exemplary embodiment 16 of the
present invention.
FIG. 20 shows a transverse sectional view for illustrating the
actions of an ultrasonic fluid measurement instrument according to
exemplary embodiment 16 of the present invention.
FIG. 21 shows a transverse sectional view for illustrating the
actions of an ultrasonic fluid measurement instrument according to
exemplary embodiment 17 of the present invention.
FIG. 22 shows a transverse sectional view for illustrating the
actions of an ultrasonic fluid measurement instrument according to
exemplary embodiment 18 of the present invention.
FIG. 23 shows a transverse sectional view for illustrating the
actions of an ultrasonic fluid measurement instrument according to
exemplary embodiment 19 of the present invention.
DETAILED DESCRIPTION OF THE INVENTION
Hereinafter, a description will be made for exemplary embodiments
of the present invention, referring to drawings.
Here, the drawings are schematic and do not show respective
dimensional positions correctly. The frequency of ultrasonic waves
in the present invention ranges from 20 KHz to 1 MHz, where 500 KHz
is desirable.
Exemplary Embodiment 1
As shown in FIGS. 1 and 2, the intermediate part of rectangular
measurement part 1 with its rectangle cross-section is partitioned
by a plurality of partition boards 2 at its short side.
In this way, a large number of split channels 3 are formed in
parallel with the long side, the collection of which composes
multilayer channel 4. This embodiment shows 4-layer structure.
Each split channel 3 is flat with a given aspect ratio so that the
fluid flow will become a two-dimensional flow, namely a laminar
flow.
In measurement part 1, approach channels 5 and 6 are formed at the
upstream and downstream sides of multilayer channel 4, with a given
length and additionally with a fixed size of cross-section in the
flow direction.
Fluid channel 7, including measurement part 1, has bent parts 8 and
9, and is equipped with upstream chamber 10 and downstream chamber
11, forming a U-shape together with above-mentioned measurement
part 1.
The respective distal ends of approach channels 5 and 6 in the
above-mentioned measurement part 1 are positioned so as to project
through bent parts 8 and 9 of upstream chamber 10 and downstream
chamber 11, respectively. Folding-back plates 12 and 13 are
respectively arranged at a further upstream part than upstream
chamber 10 and at a further downstream part than downstream chamber
11, of fluid channel 7.
Recesses 14 and 15 formed on the short side wall of measurement
part 1 are provided with ultrasonic transmitter-receivers 16 and 17
each made of a pair of ultrasonic oscillators arranged so as to
face to each split channel 3. The ultrasonic propagation path
between ultrasonic transmitter-receivers 16 and 17 is provided so
as to obliquely cross the direction of the fluid stream flowing
through each split channel 3.
Recesses 14 and 15 provided with the above-mentioned ultrasonic
transmitter-receivers 16 and 17 are covered with
ultrasonic-transparent members 18 and 19 made of a perforated plate
such as wire mesh or punching metal, at the side of split channels
3, so as not to form steps on the channel walls.
Arithmetic unit 20 calculates flow velocity of fluid, or flow
volume by multiplying the flow velocity calculated by the
cross-sectional of area of each split channel 3, and by a given
correction coefficient, according to the propagation time of
ultrasonic waves generated by a pair of ultrasonic
transmitter-receivers 16 and 17.
Thickness (d) of partition boards 2 is set to be shorter (e.g., 0.3
mm) than the wavelength of ultrasonic waves (e.g., 0.7 mm).
The length (L) of approach channels 5 and 6 in the flow direction
of the fluid is set to be longer than the height (H) of the short
side.
In the above-mentioned arrangement, the velocity of fluid flowing
in from one end of U-shaped fluid channel 7 is decelerated and
uniformized in upstream chamber 10, and the fluid flows in through
the periphery of projected approach channel 5. This way implements
further uniformized flow.
Approach channel 5, long in the flow direction, further smoothes
the flow, allowing the fluid to evenly flow into each split channel
3 of multilayer channel 4. More specifically, with approach channel
5 longer than the height in the length direction, a fluid flowing
in through the inlet of approach channel 5 at an angle is diverted
in the length direction.
Therefore, fluid is to evenly flow into each split channel 3 of
multilayer channel 4. As a result ultrasonic waves propagate
through even streams in each split channel 3, allowing the
propagation time generated by the stream to be measured
accurately.
Meanwhile, split channels 3 are very narrow (e.g., between 1 mm and
4 mm, optimally approximately 2 mm), and thus ultrasonic waves pass
through the entire channels from the bottom to the top, enabling
measurement without being influenced by the distribution of flow
velocity.
Consequently, the correction coefficient (referred to as "flow
volume coefficient" as well) for converting propagation time to
flow volume remains constant all through from small flow volumes to
large ones.
In addition, without being influenced by the distribution of flow
velocity, the correction coefficient remains constant regardless of
type of fluid (e.g., air, 13A-type city gas, liquefied petroleum
gas).
Split channels 3 are so narrow that ultrasonic waves propagate
through the uneven stream distribution in the channel even if
pulsatile flow occurs. Consequently, the propagation time agrees
with the time during which ultrasonic waves are influenced by the
uneven pulsatile flow, enabling the pulsatile flow to be accurately
measured.
Further, the downstream side of multilayer channel 4 has a
symmetric shape with the upstream side, and thus reverse flow can
be measured accurately as well, even if reverse flow occurs due to
pulsatile flow. Therefore, measurement of flow volume can be
performed in a highly accurate manner for both forward and reverse
pulsatile flows.
In a gas meter, for example, the flow volume of gas can be measured
accurately because measurement can be performed for both forward
and reverse pulsatile flows.
Here, if reverse flow cannot occur, approach channel 6 at the
downstream side may be omitted.
Partition boards 2, with thickness (d) shorter than the wavelength
of ultrasonic waves are resistant to inhibiting propagation of
ultrasonic waves, allowing transmitting and receiving with a high
signal level. Consequently, ultrasonic waves are transmitted and
received accurately with a high signal-to-noise ratio, resulting in
a highly accurate measurement of flow volume.
The side of multilayer channel 4, equipped with ultrasonic
transmitter-receivers 16 and 17, is formed with recesses 14 and 15
where the ultrasonic transmitter-receivers 16 and 17 are mounted.
The side is provided with ultrasonic-transparent members 18 and 19
to cover it, without steps in parallel with the wall surface of the
channel. Therefore, the ultrasonic-transparent members 18 and 19
prevent the stream from flowing into recesses 14 and 15 and
generating a turbulent flow. In this way, flow volume can be
measured with a high accuracy in a wide range of flow volume, and a
whirlpool is suppressed against pulsatile flow, allowing flow
volume to be measured accurately.
If wire mesh is adopted as the ultrasonic-transparent members 18
and 19, the mesh size is to be set in the range from 50 to 500
meshes (optimally 120 to 200 meshes). In this way, sound waves can
be efficiently transmitted at ultrasonic frequencies with their
wavelength of approximately 0.7 mm to transmit and to receive
ultrasonic waves with a high sensitivity, increasing accuracy in
measuring flow volume.
Odd number (for example, three) of partition boards 2 partitioning
split channels 3 are arranged at even intervals, where one of them
centrally located is to be positioned in the center of the
ultrasonic transmitting and receiving regions of ultrasonic
transmitter-receivers 16 and 17.
The sensitivity distribution of transmitter-receivers 16 and 17
generally represents highest in sensitivity at its center, and thus
dividing the sensitivity distribution so that one of partition
boards 2 will be positioned at the highest part allows ultrasonic
waves to propagate through each split channel 3 evenly.
Because the transmitting and receiving is accomplished by the
ultrasonic waves being evenly distributed, measurement can be
performed accurately at each split channel 3, allowing the
measurement of flow volume to be highly accurate.
Here, when an even number of partition boards 2 is arranged, one of
them can be positioned in the center of the ultrasonic transmitting
and receiving regions of ultrasonic transmitter-receivers 16 and
17, by adjusting mutual intervals. In this case, split channels 3
obviously need to satisfy the requirement that fluid flow
two-dimensionally.
Here, partition boards 2 partitioning split channels 3 are
desirably surface-treated with a nonviscous material. As a
nonviscous material, fluorine oil, silicone oil, or the like is
used. Alternatively, fluorocarbon resin may used for partition
boards 2, or may be laminated on partition boards 2. In this way,
foreign matter is prevented from attaching to a narrow gap,
improving durability and reliability. Further, the above-mentioned
surface treatment may be applied not only to partition boards 2,
but to the entire split channels 3, where obviously fluorocarbon
resin may be used in the same way.
Exemplary Embodiment 2
FIG. 3 shows partition boards 2 inclined so that the lower part
will be positioned at the downstream side.
As a result from the partition boards 2 being inclined in this way,
foreign matter on them flows downstream due to the inclination and
a stream through approach channel 6 to downstream chamber 11, and
thus foreign matter is resistant to accumulating in multilayer
channel 4.
Here, the description is made for the arrangement in which the
boards are inclined downstream. However, the same effect in which
foreign matter falls into upstream chamber 10, is expected when
pulsatile flow occurs, even if inclined upstream.
Additionally, the projected distal end of approach channel 5
prevents foreign matter that has fallen into the above-mentioned
upstream chamber 10 from flowing back to split channels 3,
implementing the channel with a small amount of foreign matter
clogged.
Exemplary Embodiment 3
FIG. 4 shows exemplary embodiment 3 in which propagation of
ultrasonic waves through each split channel 3 is further improved.
More specifically, ultrasonic transmitter-receivers 16 and 17 are
provided with piezoelectric oscillators 21 and acoustic matching
layers 22, fixed on the inner and outer top surfaces of case 40,
respectively, by means of bonding or the like.
Further, the above-mentioned piezoelectric oscillator 21 is divided
by plural slits 23 that are arranged in the same direction as and
additionally in parallel with the above-mentioned partition boards
2. Here, ultrasonic transmitter-receivers 16 and 17 have the same
arrangement, and thus the description is made for only ultrasonic
transmitter-receiver 17 in this example.
The same number of slits 23 are provided as that of partition
boards 2 partitioning split channels 3 so as to correspond to each
other.
Accordingly, it is obvious that ultrasonic waves can be efficiently
transmitted through each split channel 3. Moreover, the part with a
high sensitivity can face to split channels 3, and that with a low
sensitivity to partition boards 2.
The interval between slits 23 with roughly the same length as the
thickness of partition boards 2 allows ultrasonic waves to
propagate through split channels 3 between partition boards 2 more
smoothly.
Therefore, ultrasonic waves pass through each thin layer evenly,
allowing flow velocity at each layer to be measured accurately.
Consequently, the correction coefficient for converting propagation
time to flow volume (also referred to as "flow volume coefficient")
remains constant (e.g., 1) all through from small flow volumes to
large ones, namely a flat characteristic.
As a result that ultrasonic waves propagate through the entire
cross-sectional area of each split channel 3, flow velocity can be
measured accurately, even for reverse flow due to pulsatile flow in
the same way. Highly accurate measurement can be thus performed for
flow volume of both forward and reverse flows.
In a gas meter, for example, the flow volume of gas can be measured
accurately because measurement can be performed for both forward
and reverse and pulsatile flows.
Exemplary Embodiment 4
Next, FIG. 5 shows an example in which slits 23 formed in
piezoelectric oscillator 21 of ultrasonic transmitter-receivers 16
and 17 are positioned orthogonally to partition boards 2. The other
parts of the arrangement of piezoelectric oscillator 21 are the
same as in FIG. 4, and the arrangement of ultrasonic
transmitter-receivers 16 and 17 is the same. Therefore, this
example will describe only ultrasonic transmitter-receiver 17.
As a result that slits 23 of piezoelectric oscillator 21 are
provided in a direction orthogonal to partition boards 2 as
mentioned above, ultrasonic waves can propagate through other split
channels 3 even if one of the split channels 3 is defective,
implementing highly reliable measurement.
Further, the propagation of ultrasonic waves through flat split
channels 3 enables the flow volume coefficient to approximate 1,
and thus a flat characteristic is available from small flow volumes
to large flow volumes.
Exemplary Embodiment 5
FIG. 6 shows an example in which both upstream end sides of
partition boards 2 are projected upstream. This arrangement
suppresses influx to the vicinity of the channels at both sides of
split channels 3, increases the flow velocity in the central part,
and reduces the influence by uneven streams near the boundary
layers, further increasing measurement accuracy.
Meanwhile, both downstream end sides of partition boards 3 are
projected downstream. This arrangement suppresses influx to the
vicinity of the channels at both sides of split channels 3 even
with pulsatile flow, increases the flow velocity in the central
part, and reduces the influence by uneven streams near the boundary
layers, further increasing measurement accuracy.
Exemplary Embodiment 6
FIG. 7 shows an example in which, in a direction opposite to that
in above-mentioned FIG. 6, both upstream end sides of partition
boards 2 are retreated downstream. This arrangement reduces foreign
matter clogged near the center of split channels 3, increasing
durability. In the same way, both downstream end sides of partition
boards 3 are retreated upstream to reduce foreign matter clogged
near the center of split channels 3, even with pulsatile flow, to
increase durability.
Exemplary Embodiment 7
The arrangement shown in FIG. 8 is equipped with three partition
boards 2a through 2c in which central partition board 2b extends
forward beyond other partition boards 2a and 2c. First, this
arrangement partitions the channel in measurement part 1 into two
split channels 3a and 3b. Next, short partition boards 2a and 2c
further partition two split channels 3a and 3b into four split
channels 3c, 3d, 3e, and 3f.
In such an arrangement, the fluid with its stream uniformized
through approach channel 5 is split into split channels 3a and 3b
first, and then into split channels 3c, 3d, 3e, and 3f again. Each
stream flows in a laminar flow state through approach channel 6
into downstream chamber 11.
Here, it is assumed that partition boards 2a, 2b, and 2c have the
same length and fluid is immediately split into four split channels
3c, 3d, 3e, and 3f. In this case, in the distribution of the flow
velocity of fluid flowing through measurement part 1, the flow
velocity tends to be high in split channels 3d and 3e, near the
inner part; and low in split channels 3c and 3f, near the external
wall, thus strongly influenced by the distribution of the flow
velocity in approach channel 5.
Here, as in FIGS. 8 and 9, long partition board 2b provided
centrally and short partition boards 2a and 2c provided near the
external wall cause the following. That is, substantively
increasing channels, such as splitting into two split channels 3a
and 3b first, and then into four split channels 3c, 3d, 3e, and 3f,
from upstream to downstream in a region for measurement by an
ultrasonic transmitter-receiver, causes the flow velocity
distribution of fluid to be uniformized.
According to this embodiment as mentioned above, a stream is split,
and thus each flow velocity is uniformized through four split
channels 3c, 3d, 3e, and 3f each divided, to reduce influence by
the flow velocity distribution of fluid in approach channel 5,
implementing a highly accurate ultrasonic flowmeter.
Further, the uniformization of flow velocity distribution using
partition boards 2a, 2b, and 2c enables accurate measurement over a
wide cross-sectional area of a stream independently of a fluid
type.
In this embodiment, the description is made for a region measured
by the ultrasonic transmitter-receiver of measurement part 1.
However, the number of split channels may be changed by changing
the length of partition boards 2a, 2b, and 2c for the downstream
side as well. In this case, even for reverse flow such as pulsatile
flow, the flow velocity of the pulsatile flow is desirably
uniformized at the downstream side, allowing accurate
measurement.
Here, this embodiment uses three partition boards 2a, 2b, and 2c to
finally divide into four split channels 3c, 3d, 3e, and 3f.
However, increasing or decreasing the number of split channels by
changing the number of partition boards brings the same effect.
When increasing or decreasing the number of split channels, it is
desirable to increase partition boards so that they will be
arranged symmetrically with respect to the partition board provided
at the center of the channel to obtain a uniform flow velocity with
the stream distributed.
More preferably, the number of split channels is increased stepwise
from upstream to downstream of the channel and each cross-sectional
area of the split channels is equalized at each step to distribute
the stream evenly.
Exemplary Embodiment 8
In this embodiment, as shown in FIG. 10, the channel in measurement
part 1 is divided into six split channels 3g, 3h, 3i, 3j, 3k, and
3m by five partition boards 2d, 2e, 2f, 2g, and 2h.
Then, as a result that three partition boards 2e, 2f, and 2g
centrally positioned are extended beyond other partition boards 2d
and 2h externally positioned, two split channels 3i and 3j
centrally located are set to be longer than other split channels
3g, 3h, 3k, and 3m externally located.
With this arrangement, split channels 3i and 3j centrally located
become longer than other split channels 3g, 3h, 3k, and 3m, and
thus the resistance when fluid flows through split channels 3i and
3j becomes higher than that through other split channels 3g, 3h,
3k, and 3m.
Consequently, the flow velocity is uniformized both in split
channels 3i and 3j with a high flow velocity and in split channels
3g, 3h, 3k, and 3m with a low one.
Here, the number of split channels is not limited at all as long as
it corresponds to the flow velocity distribution, and it may be
general that the length of the split channels be changed
stepwise.
Exemplary Embodiment 9
In this embodiment, as shown in FIG. 11, the channel of measurement
part 1 is divided into six split channels 3n, 3o, 3p, 3q, 3r, and
3s by five partition boards 2i, 2j, 2k, 2m, and 2n, all with the
same length, where the cross-sectional area of split channels is
expanded stepwise from the center to external part.
Changing the cross-sectional area of split channels 3n through 3s
is implemented by adjusting adjacent intervals of partition boards
2i through 2n.
According to this embodiment as mentioned above, the
cross-sectional area of split channels 3n through 3s is incremented
from the center part to external. Consequently, even if the flow
velocity near the center in approach channel 5 is high, the flow
velocity is uniform in each split channel 3n through 3s, because
the cross-sectional area (i.e., corresponding to fluid resistance)
of split channels 3n through 3s is set according to the
velocity.
The uniformization of the flow velocity in each split channel 3n
through 3s allows implementing highly accurate measurement of flow
volume.
Here, changing the cross-sectional area of each split channel 3n
through 3s can be implemented by changing the thicknesses of
partition boards 2o, 2p, and 2q, as shown in FIG. 12.
Exemplary Embodiment 10
In this embodiment, as shown in FIG. 12, four split channels 3t,
3u, 3v, and 3w are provided, and the thicknesses of partition
boards 2o, 2p, 2q is to be changed.
Here, in this embodiment, the cross-sectional area is incremented
from the center part to external of measurement part 1. However,
how to change the cross-sectional area may not be restricted at all
as long as the size of the area corresponds to the flow velocity
distribution in the approach channel.
Further, the cross-sectional area and length of the split channels
may be changed simultaneously according to the flow velocity
distribution. In other words, the length of a split channel with a
high flow velocity of fluid is to be longer than the others and
additionally its cross-sectional area is to be smaller than the
others.
At least one of the changes in cross-sectional area and length of
split channels is generally made stepwise. Further, the length may
be decremented and additionally the cross-sectional area may be
incremented from a channel with a low flow velocity to a large flow
velocity.
Exemplary Embodiment 11
In this embodiment, as shown in FIGS. 13 and 14, measurement part 1
equipped with multilayer channel 4 is structured separately from
fluid channel 7.
More specifically, four split channels 3a through 3d composing
multilayer channel 4 are partitioned by three partition boards 2a
through 2c. Measurement part 1 is rectangular with its rectangle
cross-section and has openings 24 and 25 at its short side
wall.
Meanwhile, ultrasonic transmitter-receivers 16 and 17 are arranged
at the side of fluid channel 7 where above-mentioned measurement
part 1 is inserted. For this reason, recesses 14 and 15 are formed
at the short sides facing each other, of fluid channel 7 for
installing above-mentioned ultrasonic transmitter-receivers 16 and
17 therein.
When measurement part 1 is set to fluid channel 7, recesses 14 and
15 positionally conform to openings 24 and 25, respectively, to
form an ultrasonic propagation path in each split channel 3 through
opens 24 and 25.
The above-mentioned openings 24 and 25 are provided with
ultrasonic-transparent members 18 and 19 to cover them, made of a
perforated plate such as wire mesh and punching metal, so that
fluid will not flow into recesses 14 and 15. (Here, the figure
shows one facing to ultrasonic transmitter-receiver 16 at the
upstream side, as a representative.)
The propagation time of ultrasonic waves between ultrasonic
transmitter-receivers 16 and 17 is measured by measurement
controller 26, and arithmetic unit 20 calculates flow velocity
according to the propagation time, and flow volume according to the
velocity when needed. These measurement controller 26, arithmetic
unit 20, and others are driven on battery (power supply unit) 27
such as a lithium battery.
The inlet side of fluid channel 7 is connected to valve plug 28
that closes at the time of earthquake and the like. Drive unit 29
of valve plug 28, measurement controller 26, arithmetic unit 20,
and others are arranged on an area enclosed by a U-shaped channel
component material, in a compact structure on the whole.
The ultrasonic propagation path between ultrasonic
transmitter-receivers 16 and 17 faces to central partition board
2b, mainly to central adjacent two split channels 3b and 3c.
In the above-mentioned arrangement, a description will be made for
the flow volume measurement of fluid.
First, ultrasonic waves are generated from ultrasonic
transmitter-receiver 16 at the upstream side in the forward
direction of the stream and additionally so as to obliquely cross
the stream.
These ultrasonic waves propagate through the fluid stream at the
velocity of sound, are detected by ultrasonic transmitter-receiver
17 at the downstream side, and then converted to an electric
signal. Next, the electric signal is amplified by the amplifier of
measurement controller 26, and compared to a reference signal by
the comparator to detect that an ultrasonic signal has been
received.
The variation in this compared signal is sent to the repetition
part, and transmitted again by the trigger part via the delay
part.
This repetition completes with the count set in the count setting
part.
The timer part resets its timer when a first trigger signal is
transmitted, and measures the time until when the repetition
completes.
When the transmitting of the ultrasonic waves from upstream to
downstream ends, the switching part switches the direction of
transmitting and receiving.
Transmission is performed from ultrasonic transmitter-receiver 17
at the downstream side to ultrasonic transmitter-receiver 16 at the
upstream side, namely from downstream to upstream, and in the same
way as the above, transmission is repeatedly performed to measure
the time. Arithmetic unit 20 calculates flow velocity from the time
difference between the time from upstream to downstream and that in
the reverse direction, using an arithmetic expression such as
reciprocal difference of propagation time, and flow volume when
needed.
Valve plug 28 is to be closed at the time of abnormal fluid flow,
earthquake, or others.
Meanwhile, as mentioned above, measurement part 1, structured
separately from fluid channel 7, can be processed independently.
Further, a highly accurate measurement part is easily available,
resulting in ensuring a precise response to a specification
change.
Next, a description will be made for how fluid flows into
measurement part 1. Fluid passes through valve plug 28 and then
reaches upstream chamber 10. Next, fluid is rectified in approach
channel 5 of measurement part 1, to flow into split channels 3a
through 3d.
Therefore, fluid flows stably and evenly through split channels 3a
through 3d, dispensing with measuring flow velocity by ultrasonic
transmitter-receivers 16 and 17 all over split channels 3a through
3d, and thus the original objective is achieved as long as the
measurement is mainly performed for central adjacent split channels
3b and 3c.
Each height of at least central adjacent split channels 3b and 3c
as measurement targets is set within the range of the boundary
layer region so that the measurement accuracy will not be
influenced by external factors.
If target fluid is gaseous matter such as gas, the boundary layer
of a partition board is 15 mm thick, and thus each height of split
channels 3b and 3c is to be within 30 mm in order to be within a
range of the boundary layer region.
Exemplary Embodiment 12
In this embodiment, as shown in FIG. 15, fluid flow in split
channels 3a through 3d is to be favorable. For this purpose, the
length of partition boards 2a through 2c, namely the length of
split channels 3a through 3d is to be substantially equal to the
length (W) of the ultrasonic transmitting and receiving regions of
ultrasonic transmitter-receivers 16 and 17.
This arrangement allows the length of partition boards 2a through
2c, namely that of split channels 3a through 3d, to be minimal,
proportionately reducing the drop in fluid pressure.
Exemplary Embodiment 13
In this embodiment, as shown in FIG. 16, the open edges at both
ends of measurement part 1 are to be arc-shaped or tapered. In this
way, when fluid flows into measurement part 1, the fluid smoothly
flows without generating a whirlpool or the like.
Obviously, if the end parts of partition boards 3a through 3c are
tapered in the same way, the effect will be increased.
Next, an example is shown in which a rectifying part is provided at
the open part of measurement part 1, adding ingenuity in fluid flow
into the rectifying part.
Exemplary Embodiment 14
This embodiment, as shown in FIG. 17, provides net-like members 30
and 31 such as wire mesh at the open part of measurement part
1.
With this arrangement, a turbulent flow at the upstream side is
rectified by net-like member 30 to reach approach channel 5 of
measurement part 1 in a form of a stable stream, where the stream
is further rectified in this approach channel 5.
Exemplary Embodiment 15
This embodiment, as shown in FIG. 18, adopts honeycomb-like porous
members 32 and 33 as rectifying parts. It is obvious that the same
actions and effects as those in exemplary embodiment 14 are
available.
Here, in exemplary embodiments 14 and 15, measures are taken for
stabilizing fluid flow into measurement part 1 at the time of
reverse flow. If reverse flow does not occur, measures may be taken
for stabilizing fluid flow only at the upstream side of measurement
part 1.
Exemplary Embodiment 16
In this embodiment, as shown in FIGS. 19 and 20, at least a pair of
ultrasonic transmitter-receivers 16 and 17 are arranged on one wall
part at the short side of measurement part 1 in the direction of
the fluid flow at a given interval.
Ultrasonic transmitter-receivers 16 and 17 are arranged so that
ultrasonic waves transmitted from one of them will be reflected by
the facing wall to be received by the other one. In other words,
they are set so that the ultrasonic propagation path will be
V-shaped.
Further, measurement controller 26 transmits and receives
ultrasonic waves alternately between ultrasonic
transmitter-receivers 16 and 17, measures the time difference
between the ultrasonic waves propagation time in the forward
direction and that in the backward of the fluid flow, at fixed
periods, to output the difference as a propagation time difference
signal.
The propagation time difference signal from measurement controller
26 is input to arithmetic unit 20 to calculate flow velocity, and
flow volume when needed.
In this example, ultrasonic transmitter-receivers 16 and 17 can be
installed on the same side of the wall surface and the length of
the ultrasonic propagation path can be set longer than in the case
where ultrasonic transmitter-receivers 16 and 17 are installed
facing each other and sandwiching the channel part.
This arrangement increases flexibility in mounting angle of
ultrasonic transmitter-receivers 16 and 17 and size of the channel
width, implementing flow volume measurement instrument with high
installability.
Exemplary Embodiment 17
In this embodiment, as shown in FIG. 21, the channel wall surface
at the side where ultrasonic transmitter-receivers 16 and 17 are
mounted is made of ultrasonic waves absorbent member 34 (e.g.,
resin with its minute porous surface). In this way, some components
of ultrasonic waves transmitted from the ultrasonic
transmitter-receiver in transmission do not travel along or near
the wall surface to be reflected, thus preventing impure components
of ultrasonic waves to be received.
Therefore, the receiver mainly receives reflected waves that have
passed through the propagation path in the split channels, the
waves with a small quantity of noises, improving measurement
accuracy.
Exemplary Embodiment 18
In this embodiment, as shown in FIG. 22, ultrasonic reflective
member 35 made of a material with a high reflectivity, such as a
mirror-finished metal plate, is provided on the ultrasonic
reflecting surface in the ultrasonic propagation path. In this way,
attenuation and scattering when ultrasonic waves are reflected are
reduced to enable ultrasonic waves to efficiently propagate, and to
decrease noise components in receiving waves, further improving
measurement accuracy.
Exemplary Embodiment 19
In exemplary embodiment 18, the description is made for a V-shaped
propagation path, with a single reflection on the ultrasonic
propagation path. In this embodiment, as shown in FIG. 23, the
propagation path is W-shaped, with two reflections on the facing
wall surfaces, which is available with the same effect as in
exemplary embodiment 18. In this case, it is obvious that
ultrasonic reflective member 35 may be provided on the ultrasonic
reflecting surface as well.
Here, in exemplary embodiments 6 through 19, the arrangement of
measurement part 1, more specifically the arrangement in which an
approach channel is provided in split channels and at both upstream
and downstream sides thereof, is the same as in the previous
example, and thus its description is omitted.
Further, several examples mentioned in each exemplary embodiment
can be obviously implemented singularly or in alternate
combination.
A measurement part according to the present invention is provided
with an approach channel for preliminarily rectifying fluid flowing
to split channels.
In this way, fluid as a measurement target is rectified through the
approach channel, and then is to evenly flow to the split channels,
resulting in ultrasonic propagation without variation.
A measurement part structured separately from the fluid channel
allows easily producing a complicated channel divided into plural
split channels by partition boards. In addition, dimensional
accuracy can be increased.
The approach channel is to have a fixed size of cross-section in a
direction of the fluid flow, and preferably is to be set as L>H,
where, assuming that the measurement part is rectangular with its
rectangle cross-section, H is the height of the short side, and L
is the length of the approach channel in the flow direction.
The thickness of a partition boards is set to be shorter than the
wavelength of ultrasonic waves from the ultrasonic
transmitter-receiver, for a favorable ultrasonic propagation to
split channels. Installing partition boards slopewise toward one of
the upstream and downstream sides prevents foreign matter from
accumulating.
If one of a plurality of partition boards is positioned in the
center of the ultrasonic transmitting region of the ultrasonic
transmitter-receiver, fluid measurement can be uniformized by
arranging plural split channels symmetrically to this central
partition board. Specifically, an odd number of partition boards is
used, and one partition board centrally positioned is to be located
in the center of the ultrasonic transmitting region.
If the approach channel is positioned so as to project into the
upstream chamber in the fluid channel, the fluid takes a detouring
stream form to flow into the approach channel.
Therefore, even if the inlet side of the fluid channel bends, the
above-mentioned detouring stream corrects deflecting components of
the stream, and then flows to the approach channel.
If at least a part of the path surface of the split channels is
surface-treated with a nonviscous material, foreign matter can be
prevented from attaching to the maximum extent possible.
Covering the side of the split channels of the area where the
ultrasonic transmitter-receivers have been installed with a
perforated plate eliminates turbulent flows in the split channels,
further improving measurement accuracy of ultrasonic waves. Wire
mesh with 50 to 500 meshes may be used instead of a perforated
plate.
Uniformizing fluid flow to each split channel dispenses with
setting all the split channels as measurement targets by means of
ultrasonic waves, but instead, ultrasonic waves may be transmitted
to a part of the split channels to receive ultrasonic waves that
have propagated through the fluid.
The ultrasonic transmitter-receivers are equipped with
piezoelectric oscillators with plural slits that are arranged in
parallel with the partition boards. This arrangement enables
effective propagation of ultrasonic waves.
Further, arranging the slits on the above-mentioned piezoelectric
oscillators orthogonally to the partition boards allows ultrasonic
waves to propagate through plural split channels without
variation.
In order to increase measurement accuracy by reducing the influence
by uneven streams near the boundary layer, by suppressing influx to
the vicinity of the channels at both sides of the split channels,
to increase flow velocity at the central part, some measures may be
taken, such as incrementing the number of split channels from
upstream to downstream, changing the length or cross-sectional area
of each split channel, and changing the thickness of the partition
boards. Both the length and cross-sectional area may be
changed.
The ultrasonic transmitter-receivers may be arranged facing each
other so that ultrasonic waves will propagate obliquely crossing
the split channels. Alternatively, the ultrasonic
transmitter-receivers may be arranged on the same side so that
ultrasonic waves reflected by the facing surface will propagate
obliquely crossing the split channels. For reflecting ultrasonic
waves, providing an ultrasonic reflective member on the reflecting
wall surface increases efficiency in ultrasonic waves
propagation.
The partition boards are to be spaced each other so that split
channels will be structured as boundary layer regions. The length
of split channels is to correspond to the ultrasonic transmitting
and receiving regions of the ultrasonic transmitter-receivers.
Forming the end part of the path wall of the approach channel in
the measurement part in a tapered cross-section reduces the flow
resistance of the fluid.
Providing a rectifier such as a net-like member or porous member,
at the open end part of the approach channel in the measurement
part further stabilizes the fluid flow.
INDUSTRIAL APPLICABILITY
An ultrasonic fluid measurement instrument according to the present
invention can be used for measuring flow velocity and flow volume
of gaseous fluid such as gas and liquid fluid such as water and
oil, and even for distinguishing fluid type.
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